Over the past few years, nations around the world have reeled from a series of catastrophic failures of institutional trustworthiness. As a consequence of these failures, public confidence and trust in such institutions have plummeted, leaving lingering residues of disappointment and disillusion. What causes such institutional trust failures? Why do institutions fail to fulfill the trust that is conferred on them and what, if anything, can we learn from such failures in order to avoid repeating them in the future? A primary aim of this chapter is to examine these questions. As an organizing framework or lens, I approach these questions from the vantage point of recent social psychological research on judgment and decision making in organizational contexts. Insights from such research, I argue, can inform our understanding of why institutions—despite the good intentions and earnest efforts of those who labor within them—sometimes fail to achieve the levels of trustworthy performance expected of them. A central argument advanced in this paper is that we can understand institutional trust failures as arising from a series of psychological, social, and organizational dynamics which, in concert, impede effective cooperation and coordination among interdependent decision makers. To illustrate these arguments, I examine the myriad failures of U. S. intelligence agencies to discover and preempt the September 11, 2001 terrorist attacks on American soil. Implications of this analysis for other organizations and institutions are elaborated.